She said the Government must be prepared to “junk white elephant” infrastructure projects. In a damning verdict last November, the NAO said the government’s smart meter programme had been derailed by rising costs and sliding timescales.

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The Government had expected the cost of the programme to be £11 billion just three years ago. It already believes the cost will be £500 million higher. And the NAO warned there was no chance of hitting a 2020 roll-out deadline.

In 2017, the NAO slammed HS2 for unauthorised redundancy payments to staff that smashed the cap on payouts. It showed the rail link spent £2.76 million on payouts in 2016, only £1 million of which was authorised.

Last year, the watchdog said the cost of buying land had tripled in just six years to £3.3 billion following changes to the route.